This project will develop, test, and implement novel strategies for detection of antigen-specific T cells in IDDM. Using MHC-peptide tetramers, we will analyze the peripheral T cell profile leading up to clinical onset of IDDM. This project will develop an approach to monitor and stage patients based on their TR cell autoreactivity in a manner analogous to current usage of autoantibody analysis. Aim 1 of this project will optimize the use of tetramers for detection and analysis of T cells; Aim 2 will utilize the extensive clinical resources of the DAISY program to relate the prevalence and phenotype of tetramer positive T cells to other metabolic and autoantibody markers of pre-diabetes. In Aim 3, we will pilot studiers of isolating islet antigen-specific T cells directly from pancreas of cadaveric donors; by screening donors for autoantibody profiles, this will provide a unique opportunity to isolate tissue-specific autoreactive cells for analysis. In Aim 4, we will generate and utilize novel transgenic mouse models of human anti-islet immune function, to better study the basic MHC-peptide-TCR interactions which characterize the pre-diabetic state. Overall, this project combines our successful programs in MHC tetramer analysis with our unique clinical resources of the DAISY cohorts to fill a major gap in current approaches to diabetes prevention, namely, the ability to profile autoantigen-specific T cells before, during, and after clinical intervention for diabetes prevention. Two aspects of this project- the generation of MHC tetramers and an autoimmunity-focused cadaveric processes screening program-are particularly well suited for potential expansion and dissemination within other Centers of this Autoimmunity Prevention Consortium, if desired by the steering committee.